This Invention relates to a flowmeter and, in particular, to a flowmeter that imparts a rotation to a material flow within a vibrating flow tube and measures generated gyroscopic forces to determine information regarding the material flow.
Mass flowmeters measure the mass flow rate rather than the volumetric flow rate of material. They are desirable because mass measurement is often needed for chemical reactions, recipes, custody transfer, and many other applications. Furthermore, the accuracy of mass flowmeters is not impaired by changing material density, temperature, or viscosity. Coriolis effect mass flowmeters have been on the market for at least twenty years. They are well liked because of their accuracy and their ability to measure density as well as mass. However, the high cost of Coriolis flowmeters has limited their acceptance in the market.
In prior art single straight tube Coriolis mass flowmeters, the flow tube is connected at both ends to a parallel balance bar. The flow tube is vibrated out of phase in a drive plane with respect to the balance bar at a resonant frequency. An electromagnetic driver maintains the desired amplitude of the vibration. The flow tube and balance bar act as counterbalances to each other to create a dynamically balanced structure. Velocity sensors are located at two locations along the flow tube to measure the relative velocities between the flow tube and balance bar. The velocity sensors are usually located equal distances upstream and downstream from the flow tube""s midpoint.
The vibrating flow tube imposes rotations on the upstream and downstream halves of the flow tube. The rotations stop and change direction along with the flow tube""s vibration direction. The fixed ends of the flow tube are the pivot points for the rotation and the flow tube""s longitudinal center is the point of maximum amplitude. The material moving through the rotating segments of the flow tube creates a Coriolis force that deforms the flow tube and produces a phase delay between the signals output by the velocity sensors. The phase delay between the velocity sensor output signals is proportional to the mass flow rate of the material.
The prior art single straight flow tube Coriolis mass flowmeters have a short straight flow tube that is very stiff in bending. The high stiffness results in high frequencies for the higher modes of flow tube vibration. The driven mode of vibration is usually the mode with the lowest frequency, the first bending mode. In this mode, both the flow tube and the balance bar vibrate out of phase with each other in the drive plane. The shape of this vibration mode is the same as the shape of a vibrating guitar string. The maximum vibration amplitude is in the center and the nodes (fixed points) are on the ends. The driver keeps the flow tube and balance bar vibrating and is located at the center of the flow tube and balance bar.
With straight flow tube geometry, the Coriolis force bends the flow tube in the shape of the second bending mode. The second bending mode is shaped like a stretched S and has three nodes. Two nodes are on the flow tube ends and the third node is in the center. When a flow tube vibrates in the second bending mode, the two halves of the flow tube (located on either side of the central driver) appear to be vibrating out of phase with each other. The second bending mode has a resonant frequency that is almost three times that of the first bending mode. It has a high resonant frequency because the flow tube is very stiff and it is very difficult to bend the flow tube in the shape of the second bending mode.
Coriolis forces are applied to the flow tube at the drive frequency (the resonant frequency of the first bending mode). Assuming the flow tube is horizontal and is vibrated in a vertical drive plane in the first bending mode, the Coriolis deformation of the flow tube is also in the drive plane and has the shape of the second bending mode. If material is flowing from left to right and the flow tube center is passing through the zero displacement point while traveling downward, the Coriolis force on the left half of the flow tube is in the upward direction while the Coriolis force on the right half of the flow tube is in the downward direction. When the flow tube is passing through zero displacement while traveling upward, the direction of the Coriolis force is reversed. The Coriolis force is applied to the flow tube in a sinusoidal manner (with respect to time) at the drive frequency. The Coriolis force is at its peak when the flow tube velocity is at its peak and the Coriolis force is zero when the flow tube velocity is zero as it changes direction.
The Coriolis force deflects the flow tube in the second bending mode shape but at the first mode (drive) frequency. The drive frequency is so far below the resonant frequency of the second bending mode that the maximum deflection of the flow tube due to the Coriolis force is very low. The Coriolis deflection is comparable in amplitude to the static deflection that would result from a static application of the Coriolis force. The Coriolis force due to material flow thus has to deform the stiff flow tube in a very stiff mode shape (the second bending) at a frequency (first bending) that is far removed from the second bending resonant frequency. The result is an extremely small Coriolis deflection of the flow tube and a very small phase difference between the signals produced by the two velocity sensors. A typical time delay (phase difference divided by frequency) between the two signals resulting from a maximum flow rate through a typical meter is ten microseconds. If the meter is to have no more than 0.15% error at ten percent of maximum flow, then the time delay measurement accuracy has to be better than 1.5 nanoseconds (1.5xc3x9710xe2x88x929 seconds). Accurately measuring such small time increments requires extremely sophisticated and expensive electronics.
The present invention overcomes the problems of prior Coriolis mass flowmeters by using gyroscopic force rather than Coriolis force in the material flow measurement. In accordance with one possible exemplary embodiment of the invention, a single straight tube gyroscopic flowmeter is provided that looks like the Coriolis flowmeter described above except that its flow tube has an internal helical baffle which causes the material to rotate about the longitudinal axis of the flow tube as the material flows through the tube. The rotating material causes the flow tube to act as a gyroscope. The gyroscopic meter is also different from Coriolis flowmeters in that it has its velocity sensors at the longitudinal center of the flow tube rather than upstream and downstream from the center as do Coriolis flowmeters.
In order to understand how the gyroscopic force of the rotating material can be used to measure flow, the nature of gyroscopic behavior and force will first be examined in two examples. The first example illustrates the motion (precession) that results from a torque applied to a gyroscope axle when the axle is unconstrained. The second example allows the calculation of the torque that the gyroscope axle applies to its mounting when the gyroscopic motion (precession) of the first example is prevented by constraints. It is this resultant torque that deforms the flow tube of the present invention and enables measurement of the mass flow rate.
Gyroscopes are devices having mass that rotates about an axis (called the spin axis) giving them angular momentum. Typical gyroscopes have a circular disk-like mass that is mounted on a thin axle. Conservation of the angular momentum of the rotating disc gives gyroscopes their unique properties. In understanding the present invention it is only necessary to understand how gyroscopes behave, not why they behave the way they do. Therefore, the following is limited to a description of gyroscopic behavior as pertains to the gyroscopic flowmeter of the present invention.
Consider a typical toy gyroscope having a flywheel rotating on an axle that is thirty degrees from vertical. In the first mounting condition to be considered, example 1, the top end of the gyroscope axle is free to move in all direction while the bottom of the axle is fixed at a point so that it cannot translate but it can freely rotate or pivot in all directions. If the flywheel were not rotating the gyroscope would immediately fall over due to the overturning torque of its weight times the horizontal offset of it""s center of mass from the axle bottom point. But, the rotation of the flywheel gives-the gyroscope angular momentum which resists the overturning torque. Instead, the overturning torque causes the top end of the axle to circle the vertical axis. The rate of this circular motion, called precession, increases as the top end of the gyroscope axle slowly spirals down. In summary, the overturning torque produces an angular acceleration of the top end of the axle in a circumferential direction about the vertical axis. This increasing rate of precession is the familiar increasing wobble of a toy top axis as it rotates down.
In the second mounting condition, example 2, the axle of the rotating gyroscope is initially on the Y-axis of a coordinate system (vertical) and the bottom end of the axle is again constrained in translation so that it can rotate in all directions but cannot translate. The motion of the top end of the axle is confined to the X-Y plane so that it cannot move in the Z-direction. This constraint of the top end of the axle can be visualized as a slot that is aligned with the X-axis in which the top of the axle can freely move. Applying force to the top end of the axle in the X-direction (along the slot) results in the movement of the axle upper end in the slot and the rotation of the axle in the X-Y plane about the axle bottom end (not about its rotating axis). This rotation of the axle in the X-Y plane would result in precession of the axle except that the slot prevents it. Instead, the axle top end applies a gyroscopic force, GF, to the side of the slot in the negative Z-direction. The gyroscopic force can be calculated since it is a function of the angular momentum of the gyroscope and the angular velocity at which the axle is rotated in the X-Y plane. For the present invention, it is important to note that the angular velocity of the axle in the X-Y plane causes a force GF to the axle at a right angle to the X-Y plane and also at a right angle to the gyroscope axis.
The material rotating in the flow tube of the present invention causes it to behave like a pair of gyroscopes. One flowmeter-gyroscope extends from the tube inlet to the tube midpoint while the other flowmeter-gyroscope from the tube midpoint to the tube outlet. The gyroscopic spin axes correspond to the flow tube axis and the flywheels correspond to the rotating material in each half of the flow tube. The force applied to the flow tube by the driver corresponds to the force applied to the top end of the axle in the slot of example 2. The tube vibration in the drive plane causes the flow tube center line, or spin axis, to rotate in the drive plane alternately in each direction corresponding to the slot direction. The fixed ends of the flow tube are the pivot points of the two flowmeter-gyroscope spin axes. The flow tube midpoint can be considered to be the free (or slot) end of each. The slot restraining the gyroscope axle end in example 2, however, does not exist in the flowmeter. Nor are the flowmeter-gyroscopes"" ends (tube center) free as in example 1. Instead, the flow tube stiffness resists motion of the tube center out of the drive plane but does not prevent it. The behavior of the flowmeter-gyroscopes falls between that of example 1 and that of example 2. The gyroscopic force causes a deflection of the tube center out of the drive plane that is proportional to the gyroscopic force GF. The gyroscopic force GF is in turn proportional to the mass flow rate. Thus the deflection of the flow tube out of the drive plane can be used to determine the mass flow rate of the flowing material.
The direction of the gyroscopic force GF and the deflection of the flow tube in response to the force GF is perpendicular to both the drive direction and the flow tube axis. The deflection in the gyroscopic direction reverses sign with the direction reversal of the drive vibration. The maximum tube deflection in the gyroscopic direction occurs when the tube deflection in the drive direction is passing through zero and the velocity in the drive direction is at its maximum. The flow tube deflection out of the drive plane is of the sign that conserves angular momentum. If the material rotation in the flow tube, when viewed from an end, is clockwise, then the combined drive and gyroscopic vibrations gives both flow tube halves a clockwise elliptical motion. The rate of rotation of the mass in the flow tube (proportional to the flow rate) determines the magnitude of the tube deflection in the gyroscopic direction. The flow rate determines how narrow (low flow) or wide (high flow) is the resulting ellipse. When the drive and gyroscopic forces are equal, the flow tube takes a circular path when viewed from the end.
The gyroscopic force GF and the flow tube deflection in the gyroscopic direction are proportional to the angular momentum of the rotating material flow. The angular momentum is proportional to the mass times the velocity of the mass about the spin axis. Because the product of mass and velocity determine the gyroscopic force and thus the gyroscopic deflection, the deflection is proportional to mass flow rate rather than volumetric flow rate. If the material density is low, then for a given mass flow rate, the material velocity has to be high. Conversely, for a high density material at the same mass flow rate, the material velocity has to be low. The product of density and velocity is independent of density for a given mass flow rate. Thus, the material density is irrelevant to the accurate measurement of the mass flow rate.
The gyroscopic force GF differs from the Coriolis force in three significant ways. First, as has been discussed, the gyroscopic force is lo the drive plane whereas the Coriolis force is in the drive plane. Secondly, the gyroscopic force is in the same direction for the full length of the flow tune (this will be discussed later whereas the Coriolis force changes sign in the center of thee flow tube. The uniformity of the sign of the gyroscopic force along the flow tube means that the flow tube deformation for the gyroscopic meter is of the first bending mode shape while the deformation for the Coriolis meter is of the second bending mode shape. The flow tube is much easier to bend in the first bending mode than in the second and thus for a given force, the flow tube deflects further in a gyroscopic flowmeter. Thirdly, the gyroscopic deflection is driven at or near the resonant frequency for its mode shape (the first bending mode) while the Coriolis deflection is driven at a frequency far removed from its mode shape resonant frequency (the second bending mode). Therefore, the gyroscopic deflection receives great amplification due to being driven at or near its resonant frequency while the Coriolis deflection receives very little. These three differences make the gyroscopic deflection larger than the Coriolis deflection and allow for the use of less expensive signal processing.
The magnitude of the gyroscopic force is proportional to the mass flow rate, the number of revolutions made by the helical baffle, and the vibration amplitude in the drive plane. The maximum flow rate for the flowmeter can be set so that the gyroscopic force at the maximum flow rate is approximately equal to the force that the driver applies to the flow tube. Thus the flow tube is driven in a circle at the maximum flow rate by the drive and the gyroscopic force. At lesser flow rates, the gyroscopic force is less and the circle is flattened. In order to determine the flow rate, a velocity sensor senses the velocity in the gyroscopic direction and another senses the velocity in the drive direction. The ratio of the peak velocities (peak gyroscopic/peak drive) would be the fraction of the maximum flow rate that is flowing. This velocity ratio method is easily done and avoids both the difficulty and the cost of measuring time in nanoseconds.
In accordance with other possible exemplary embodiments of the invention, a helix internal to the flow tube is not used. Instead, the flow tube is wound in the shape of a helix around a stiff rod so that the helix and the rod have a common longitudinal axis. This imparts rotation to the material flow about the longitudinal axis. Both the flow tube and rod are vibrated by a driver in a drive plane to generate gyroscopic deflections in a perpendicular plane. Alternatively, a pair or flow tubes are twisted together to form a pair of helical members with a common helical (longitudinal) axis. This imparts a rotation to the material flow in both flow tubes about the common axis. The twisted. pair is then vibrated by a driver and the material flow generates gyroscopic forces as above described. Alternatively, a single flow tube is wound to form a helix to generate a rotation to the material flow about the helical axis of the flow tube. The flow tube is the vibrated with a driver to generate gyroscopic deflections due to the rotation of the material flow.
In accordance with yet another possible exemplary embodiment, velocity sensors are positioned upstream and downstream of the flow tube center to detect the Coriolis deflections of the flow tube. The output signal from these sensors is used along with the signals of the gyroscopic sensors to provide a flowmeter that generates both gyroscopic signals and Coriolis signals for the determination of material flow output information.
An aspect of the invention is a flowmeter having a material inlet, a material outlet, and flow tube apparatus connected between said inlet and said outlet, said flowmeter being adapted to receive a material flow at said inlet and to extend said material flow through said flow tube apparatus to said outlet; said flowmeter further comprising:
a driver that cyclically deforms said flow tube apparatus by vibrating said flow tube apparatus at a drive frequency in a drive plane that includes. said longitudinal axis of said flow tube apparatus;
apparatus that imparts a rotation to said material flow in said flow tube apparatus about said longitudinal axis of said vibrating flow tube apparatus;
said apparatus for imparting includes said flow tube apparatus;
said flow tube apparatus is responsive to the cyclic deformation of said flow tube apparatus by said driver and to said rotation of said material flow that generates cyclic gyroscopic mode deformation of said flow tube apparatus in a gyroscopic plane; said cyclic gyroscopic mode deformation has an amplitude related to the magnitude of said material flow;
pickoff apparatus responsive to said gyroscopic mode cyclic deformation that generates gyroscopic signals indicative of the magnitude of said material flow; and
meter electronics responsive to the generation of said gyroscopic signals that generates output information pertaining to said material flow.
Preferably said pickoff apparatus includes a first pickoff that generates signals representing the amplitude of said cyclic gyroscopic mode deformation;
said flowmeter further includes conductor apparatus that extends said signals from said pickoff apparatus to said meter electronics;
said meter electronics is responsive to the receipt of said signals generated by said first pickoff that generates said information pertaining to said material flow.
Preferably said pickoff apparatus further includes:
a second pickoff that generates a signal representing the amplitude of said cyclic flow tube deformation in said drive plane; and
characterized in that said meter electronics includes:
apparatus responsive to the receipt of said signals generated by said first and second pickoffs that determines the ratio of the amplitude of said cyclic flow tube gyroscopic mode deformation in said gyroscopic plane to the amplitude of said cyclic flow tube deformation in said drive plane; and
apparatus responsive to said determination of said ratio that generates said output information pertaining to said material flow.
Preferably said output information includes the mass flow rate of said material is flow.
Preferably said flowmeter further includes a pickoff that measures the amplitude of said cyclic gyroscopic mode deformation of said flow tube in said gyroscopic plane; said meter electronics comprises:
apparatus that controls the amplitude of said cyclic flow tube deformation in said drive plane; and
apparatus responsive to said measurement of the amplitude of said cyclic gyroscopic mode deformation of said flow tube in said gyroscopic plane that determines the mass flow rate of said material flow.
Preferably said drive frequency is equal to the resonant frequency of said cyclic gyroscopic mode deformation amplitude to maximize said cyclic gyroscopic mode deformation in said gyroscopic plane.
Preferably said drive frequency is not equal to the resonant frequency of the gyroscopic mode deformation to alter the relationship between the material flow density and the amplitude of said cyclic gyroscopic mode deformation in said gyroscopic plane.
Preferably said flow tube apparatus comprises:
a single straight flow tube:
a helix internal to said flow tube, said helix imparts said rotation to said material flow about said longitudinal axis of said flow tube to generate said cyclic gyroscopic mode deformation in said gyroscopic plane.
Preferably said flow tube apparatus comprises:
a single flow tube having a helix shape that imparts said rotation to said material flow about said longitudinal axis of said flow tube.
Preferably said flow tube apparatus comprises:
a plurality of flow tubes twisted together about a common longitudinal axis to have an elongated shape that imparts said rotation to said material flow about said common longitudinal axis.
Preferably said flow tube apparatus comprises:
a bar and a flow tube wound on said bar to form a coil that imparts said rotation to said material flow about the common longitudinal axis of said flow tube and said
Preferably said elongated bar is substantially straight.
Preferably said bar and said flow tube are twisted together about said common longitudinal axis.
Preferably said material flow generates Coriolis forces in said drive plane on said vibrating flow tube apparatus, said Coriolis forces produce Coriolis deflections of said flow tube apparatus in said drive plane;
characterized in that said flowmeter further comprises:
pickoff apparatus on said flow tube apparatus that detect said Coriolis deflections and generate Coriolis signals containing information pertaining to said material flow;
said meter electronics is responsive to the generation of said Coriolis signals and said gyroscopic signals that generates output information pertaining to said material flow.
Preferably said flowmeter further comprises:
a balance bar parallel to said flow tube apparatus;
connecting ring apparatus connecting ends of said balance bar to said flow tube apparatus;
said driver cyclically deforms said flow tube apparatus and said balance bar in phase opposition in said drive plane at the resonant frequency of said material filled flow tube apparatus and said balance bar;
said cyclic gyroscopic mode deformation vibrates said material filled flow tube apparatus and said balance bar in said gyroscopic plane at the resonant frequency of the cyclic gyroscopic mode deformation.
Preferably said flowmeter further comprises:
a case enclosing said balance bar and said flow tube apparatus;
case ends connected to ends of said case;
ends of said flow tube apparatus project through said case ends of said case and are connected to flanges;
a first one of said flanges receives said material flow from a material source and extends said material flow through said flowmeter;
a second one of said flanges on an output end of said flow tube apparatus receives said material flow from said flow tube apparatus and extends said material flow to a destination.
Preferably said connecting ring apparatus comprises:
first and second connecting rings connecting each end of said balance bar to said flow tube apparatus; and
lateral axial projections on said connecting rings in said drive plane and affixed to lateral side walls of said flow tube apparatus that alters the resonant frequency separation of said flow tube apparatus and said balance bar deformation in said drive plane and said cyclic gyroscopic mode deformation of said flow tube apparatus and said balance bar in said gyroscopic plane.
Preferably a balance bar further including openings in the walls of said balance bar that alter the separation of the resonant frequencies of said cyclic deformation in said drive plane and said cyclic gyroscopic mode deformation of said flow tube apparatus and said balance bar in said gyroscopic plane.
Preferably said method comprises the steps of:
cyclically deforming said flow tube apparatus by vibrating said flow tube apparatus in said drive plane;
imparting said rotation to said material flow about said longitudinal axis of said flow tube apparatus in response to said material flow, said rotation causes said cyclic gyroscopic mode deformation of said flow tube apparatus in said gyroscopic plane;
generating signals indicative of the magnitude of said material flow in response to said generation of said cyclic gyroscopic mode deformation; and
operating said meter electronics in response to said generation of said signals that generates output information pertaining to said material flow.
Preferably said step of said generating output signals includes the step of generating signals representing the amplitude of said cyclic gyroscopic mode deformation in said gyroscopic plane.
Preferably the steps of:
determining the amplitude of said flow tube apparatus cyclic deformation in said drive plane;
determining the ratio of the amplitude of said flow tube apparatus cyclic gyroscopic mode deformation in said gyroscopic plane to the amplitude of said flow tube apparatus cyclic deformation in said drive plane; and
in response to said determination of said ratio, generating said output information pertaining to said material flow.
Preferably the steps of:
controlling the amplitude of said flow tube apparatus cyclic deformation in said drive plane;
measuring the amplitude of said cyclic gyroscopic mode deformation of said flow tube apparatus in said gyroscopic plane; and
operating said meter electronics in response to said measurement that generates said output information pertaining to said material flow.
Preferably operating said flowmeter so that said resonant frequency of said cyclic flow tube apparatus deformation in said drive plane is equal to the gyroscopic mode deformation resonant frequency to maximize the amplitude of said cyclic gyroscopic mode deformation in said gyroscopic plane.
Preferably operating said flowmeter so that said resonant frequency of said cyclic flow tube apparatus deformation in said drive plane is not equal to the gyroscopic mode deformation resonant frequency to alter the relationship between the density of said material flow and the amplitude of said cyclic gyroscopic mode deformation in said gyroscopic plane.
Preferably said flow tube apparatus comprises a single straight flow tube:
said method includes the step of inserting a helix internal to said flow tube to impart said rotation to said material flow about the longitudinal axis of said flow tube.
Preferably said flow tube apparatus comprises a single flow tube and wherein said method further includes the step of operating said flowmeter with said flow tube formed to define a coil spring shape that imparts said rotation to said material flow about the longitudinal axis of said flow tube.
Preferably said flow tube apparatus comprises a plurality of flow tubes and wherein said method further includes the steps of;
twisting said plurality of flow tubes together about a common longitudinal axis to define an elongated shape that imparts said rotation to said material flow.
Preferably said flow tube apparatus comprises a single flow tube and wherein. said method further includes the step of winding said flow tube on an elongated bars to form a coil that imparts said rotation to said material flow about a longitudinal axis common to said flow tube and said bar.
Preferably said material flow generates Coriolis forces in said drive plane on said vibrating flow tube apparatus, said Coriolis forces produce periodic Coriolis deflections of said flow tube apparatus in said drive plane; characterized in that said method further comprises;
operating pickoffs on said flow tube apparatus that detect said Coriolis deflections and generate output signals pertaining to said material flow;
operating said meter electronics in response to the generation of said Coriolis signals and said gyroscopic signals that generates output information pertaining to said material flow.
Preferably said flowmeter comprises a balance bar parallel to said flow tube apparatus;
connecting ring apparatus connecting ends of said balance bar to said flow tube apparatus;
said method further includes:
operating said driver to vibrate said flow tube apparatus and said balance bar in phase opposition in said drive plane at the resonant frequency of said material filled flow tube apparatus and said balance bar;
operating said flowmeter so that said gyroscopic forces vibrate said material filled flow tube apparatus and said balance bar in said gyroscopic plane at the resonant frequency of said material filled flow tube apparatus and said balance bar in said gyroscopic mode of vibration.
Preferably said gyroscopic plane is perpendicular to said drive plane and to said longitudinal axis of said flow tube.
Another aspect is that said pickoff means includes a first pickoff that generates signals representing the amplitude of said gyroscopic mode vibrations;
said flowmeter further includes conductor means that extends said signals from said pickoff means to said meter electronics;
said meter electronics is responsive to the receipt of said signals generated by said first pickoff for generating said information pertaining to said material flow.
Another aspect is that said pickoff means further includes:
a second pickoff for generating a signal representing the amplitude of said flow tube drive vibrations in said drive plane; and
characterized in that said meter electronics includes:
means responsive to the receipt of said signals generated by said first and second pickoffs for determining the ratio of the amplitude of said flow tube gyroscopic mode vibrations in said gyroscopic plane to the amplitude of said flow tube drive mode vibrations in said drive plane; and
means responsive to said determination of said ratio for generating said output information pertaining to said material flow.
Another aspect is that said output information includes the mass flow rate of said material flow.
Another aspect is that said flowmeter further includes a pickoff for measuring the amplitude of said gyroscopic mode vibrations of said flow tube in said gyroscopic plane; said meter electronics comprises:
means for controlling the amplitude of said flow tube drive mode vibrations in said drive plane; and
means responsive to said measurement of the amplitude of said gyroscopic mode vibrations of said flow tube in said gyroscopic plane for determining the mass flow rate of said material flow.
Another aspect is that said drive frequency is equal to the resonant frequency of said gyroscopic vibration mode to maximize said gyroscopic mode vibrations in said gyroscopic plane.
Another aspect is that said drive frequency is not equal to the resonant frequency of the gyroscopic vibration mode to alter the relationship between the material flow density and the amplitude of said gyroscopic mode vibrations in said gyroscopic plane.
Another aspect is that said flow tube means comprises:
a single straight flow tube:
a helix internal to said flow tube, said helix imparts said spin to said material flow about said longitudinal axis of said flow tube to generate said gyroscopic mode vibrations in said gyroscopic plane.
Another aspect is that said flow tube means comprises:
a single flow tube having a coil spring shape that imparts said spin to said material flow about said longitudinal axis of said flow tube.
Another aspect is that said flow tube means comprises:
a plurality of flow tubes twisted together about a common longitudinal axis to have an elongated shape that imparts said spin to said material flow about said common longitudinal axis.
Another aspect is that said flow tube means comprises:
a bar and a flow tube wound on said bar to form a coil that imparts said spin to said material flow about the common longitudinal axis of said flow tube and said bar.
Another aspect is that said elongated bar is substantially straight.
Another aspect is that said bar and said flow tube are twisted together about said common longitudinal axis.
Another aspect is that said material flow generates Coriolis forces in said drive plane on said vibrating flow tube means, said Coriolis forces produce Coriolis deflections of said flow tube means in said drive plane; characterized in that said flowmeter further comprises;
pickoff means on said flow tube means that detect said Coriolis deflections and generate Coriolis output signals containing information pertaining to said material flow;
said meter electronics is responsive to the generation of said Coriolis signals and said gyroscopic signals for generating output information pertaining to said material flow.
Another aspect is that said flowmeter further comprises:
a balance bar parallel to said flow tube means;
connecting ring means connecting ends of said balance bar to said flow tube means;
said driver vibrates said flow tube means and said balance bar in phase opposition in a drive vibration mode in said drive plane at the resonant frequency of said material filled flow tube means and said balance bar;
said gyroscopic mode vibrations vibrate said material filled flow tube means and said balance bar in said gyroscopic plane at the resonant frequency of the gyroscopic mode vibrations of said material filled flow tube means and said balance bar.
Another aspect is that said flowmeter further comprises:
a case enclosing said balance bar and said flow tube means;
case ends connected to ends of said case;
ends of said flow tube means project through said case ends of said case and are connected to flanges;
a first one of said flanges receives said material flow from a material source and extends said material flow through said flowmeter;
a second one of said flanges on an output end of said flow tube means receives said material flow from said flow tube means and extends said material flow to a destination.
Another aspect is that said connecting ring means comprises:
first and second connecting rings connecting each end of said balance bar to said flow tube means; and
lateral axial projections on said connecting rings and affixed to lateral side walls of said flow tube means for altering the resonant frequency separation of said drive mode vibration and said gyroscopic mode vibrations of said flow tube means and said balance bar.
Another aspect includes openings in the walls of said balance bar that alter the separation of the resonant frequencies of said drive mode vibrations and said gyroscopic mode vibrations of said flow tube means and said balance bar.
Another aspect includes a method of operating said flowmeter comprising the steps of:
vibrating said flow tube means in said drive plane;
imparting said spin to said material flow about said longitudinal axis of said flow tube means;
said spin causes said gyroscopic mode vibrations of said flow tube means in said gyroscopic plane;
generating output signals indicative of the magnitude of said material flow in response to said generation of said gyroscopic mode vibrations; and
operating said meter electronics for generating output information pertaining to said material flow.
Another aspect is that said step of said generating output signals includes the step of generating signals representing the amplitude of said gyroscopic mode vibrations in said gyroscopic plane.
Another aspect includes the steps of:
determining the amplitude of said flow tube means drive mode vibrations in said drive plane;
determining the ratio of the amplitude of said gyroscopic mode vibrations in said gyroscopic plane to the amplitude of said flow tube means drive mode vibrations in said drive plane; and
in response to said determination of said ratio, generating said output information pertaining to said material flow.
Another aspect includes the steps of:
controlling the amplitude of said flow tube means drive mode vibrations in said drive plane;
measuring the amplitude of said gyroscopic mode vibrations of said flow tube means in said gyroscopic plane; and
operating said meter electronics in response to said measurement for generating said output information pertaining to said material flow.
Another aspect includes the step of operating said flowmeter so that said drive plane vibration mode resonant frequency is equal to the gyroscopic vibration mode resonant frequency to maximize the amplitude of said gyroscopic mode vibrations in said gyroscopic plane.
Another aspect includes the step of operating said flowmeter so that said drive vibration mode resonant frequency is not equal to the gyroscopic mode resonant frequency of said mode vibrations to alter the relationship between the density of said material flow and the amplitude of said gyroscopic mode vibrations in said gyroscopic plane.
Another aspect is that said flow tube means comprises a single straight flow tube:
said method includes the step of inserting a helix internal to said flow tube to impart said spin to said material flow about the longitudinal axis of said flow tube.
Another aspect is that said flow tube means comprises a single flow tube and wherein said method further includes the step of operating said flowmeter with said flow tube formed to define a coil spring shape that imparts said spin to said material flow about the longitudinal axis of said flow tube.
Another aspect is that said flow tube means comprises a plurality of flow tubes and wherein said method further includes the steps of:
twisting said plurality of flow tubes together about a common longitudinal axis to define an elongated shape that imparts said spin to said material flow.
Another aspect is that said flow tube means comprises a single flow tube and wherein said method further includes the step of winding said flow tube on an elongated bar to form a coil that imparts said spin to said material flow about a longitudinal axis common to said flow tube and said bar.
Another aspect is that said material flow generates Coriolis forces in said drive plane on said vibrating flow tube means, said Coriolis forces produce periodic Coriolis deflections of said flow tube means in said drive plane; characterized in that said method further comprises:
operating pickoffs on said flow tube means that detect said Coriolis deflections and generate output signals pertaining to said material flow;
operating said meter electronics in response to the generation of said Coriolis signals and said gyroscopic signals for generating output information pertaining to said material flow.
Another aspect is that said flowmeter comprises a balance bar parallel to said flow tube means;
connecting ring means connecting ends of said balance bar to said flow tube means;
said method further includes:
operating said driver to vibrate said flow tube means and said balance bar in phase opposition in said drive plane at the resonant frequency of said material filled flow tube means and said balance bar;
operating said flowmeter so that said gyroscopic forces vibrate said material filled flow tube means and said balance bar in said gyroscopic plane at the resonant frequency of said material filled flow tube means and said balance bar in said gyroscopic mode of vibration.